Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $193.31   5.853%   $204.6244   $204.62   $204.60   $204.60  
  Purchase #2 $96.39   5.837%   $102.0163   $102.02   $102.00   $102.00  
  Purchase #3 $248.85   9.800%   $273.2373   $273.24   $273.25   $273.20  
  Purchase #4 $235.28   6.774%   $251.2179   $251.22   $251.20   $251.20  
  Purchase #5 $100.29   3.826%   $104.1271   $104.13   $104.15   $104.10  
  Purchase #6 $62.29   4.109%   $64.8495   $64.85   $64.85   $64.80  
  Purchase #7 $122.26   8.407%   $132.5384   $132.54   $132.55   $132.50  
  7 purchase totals = $1,058.67       $1,132.6109   $1,132.62   $1,132.60   $1,132.40